Biodegradation of Nitrilotriacetate (NTA) in Soils

Nitrilotriacetate (NTA) was biodegraded in a variety of soils as measured by total CO 2 and 14 CO 2 production from 14 C‐carboxyl‐NTA. Production of CO 2 and 14 CO 2 followed similar patterns and suggested complete degradation of NTA; 14 CO 2 production was used routinely to assay NTA dissimilation. At 40 ppm of NTA in soils receiving sewage effluent and in muck soils, maximum rates of degradation were 8 to 10 ppm/day while in mineral surface soils, they ranged from 0.5 to 6 ppm/day; the rates in subsoils were always less than for the surface soils from the same site. Degradation rates did not correlate with pH, drainage, texture, or plant cover. Rates of degradation increased from 2 to 64 ppm/day as NTA concentration was increased from 10 to 600 ppm. 14 CO 2 production from NTA did not occur anaerobically and was severely limited under microaerophilic conditions. NTA was degraded at 24 and 12.5C; it was also degraded at 2C if previously acclimatized at 12.5C. Iminodiacetate was a possible intermediate in NTA degradation while N ‐methyliminodiacetate was not.